Insights to ballast water: metagenomics as a pressing priority

Abstract

Metagenomics represents a pivotal development in genomics, offering unprecedented insights into a diverse spectrum of microorganisms, including bacteria, viruses, and fungi, that were previously challenging or impossible to study outside natural environments. Its applications span a remarkable range, from exploring cosmic entities to the depths of our oceans, incorporating numerous analyses. Yet, its utilization in the context of ballast water analysis remains scarce. This highlights the crux of the present review, which aims to showcase the need for metagenomics in ballast water analysis. As is known, ballast water is essential for maintaining ship stability under no cargo conditions or during adverse weather, with daily global movements estimated to be between 3 to 10 billion tonnes. A single bulk cargo ship can transport up to 60,000 tonnes of ballast water for a 200,000-tonne load. It is estimated that over 7,000 species are transported globally in ships' ballast water daily, posing significant ecological risks when these organisms are discharged into new environments where they can become invasive species, disrupting local ecosystems, economies, and human health. Despite the International Maritime Organization setting D-2 standard guidelines and endorsing several ballast water management practices for its safe discharge, the issue persists. This underscores the necessity of employing metagenomics to enhance the monitoring of microbial content in ballast water. The review summarizes some research conducted worldwide to analyze ballast water by metagenomics, all exhibiting diverse microbes, including potent pathogenic bacterial and viral forms. The findings support our view, making metagenomics an invaluable tool to monitor ballast water treatment effectiveness in compliance with evolving environmental regulations. Though the challenges facing metagenomic applications—namely cost, complexity, and the need for comprehensive reference databases—are significant, they will surely be surmountable considering continual technological and methodological advancements. Embracing metagenomics offers a pathway to not only address the ecological threats posed by ballast water transfers but also to safeguard the future of global shipping industries.